As facsimile machines and other automatic computer modem devices attachable to public telephone lines become less expensive and increasingly more prevalant in small businesses, there is an increasing need for means to enable the computer apparatus (F) to share a single telephone line with other telephone devices such as an automatic answering machine (A) and additional telephone sets (T).
Among facsimile (fax) machines, the most popular systems have associated telephone sets, comprising either connection means to enable a nearby telephone set to be connected to the fax (F-T), or having the telephone set actually incorporated in the housing of the fax (FT). The reason for this popularity is probably due to the fact that fax machines are usually connected to dedicated telephone lines not having additional telephone sets associated therewith. Thus, in order to carry out a voice conversation, it is necessary to have a (T) device associated with the (F) device. Such systems, however, do not allow connection of additional telephone devices such as an automatic answering machine (A) or additional remotely located telephone sets (T) to the same telephone line. If an automatic answering machine (A) is connected to the telephone line, there is no way to decide whether (A) or (F) should respond to a call. If a remotely located telephone set (T') is connected to the same telephone line, there is no way to actuate (F) from the remote location, if the call turns out to be for (F).
A number of other systems have been proposed in the past in an effort to allow various combinations of incompatible telephone devices to be connected to the same telephone line, such as the following systems:
Integrated fax and answering machine systems (with or without an additional telephone set--(FA) or (FAT)); PA1 Fax systems allowing an answering machine to be attached (F-A) or (FT-A); PA1 Interface units such as private branch exchange (PBX)-type switching systems enabling the user to actuate a selected one of these or other devices by typing additional DTMF codes (I-F-A). DTMF codes are voice-frequency electronic signals commonly known under the trademark TOUCH-TONE.
Many of these systems have proven commercially sucessful due to the strong need for solutions to this problem; however, these systems also have drawbacks. For example, the integrated (FA) or (FAT) systems such as the model KX-F120 built by PANASONIC Corp. suffer from the limitation that a user is unable to select (A) and (F) independently. This is an important consideration, because a user may favor an answering machine having a certain set of operating parameters, which may be unavailable in combination with the fax of his choice. A company may manufacture 5 different (A)'s and 5 different (F)'s, but to have the same degree of flexibility, would need to manufacture 25 different (FA)'s. In addition, some of these systems do not support the connection of additional telephone sets (T') to the same telephone line.
Some of the systems providing (F) and (A) capabilities operate by letting (F) answer first, others by letting (A) answer first, still others by letting an interface unit (if there is one) answer first. A system wherein the (F) answers first is described in U.S. Pat. No. 4,677,660 to T. Yoshida. After (F) answers, it sends out the CED and GI2 signals, waiting for a response from a calling machine. After a timeout period, if the calling party has not sent the appropriate response, the fax machine actuates the ringing of the telephone apparatus in order that voice communication may be established.
A system wherein (A) answers first is described in U.S. Pat. No. 4,584,434 to K. Hashimoto. The disclosed system includes means to allow the answering machine (TAD) to answer the ring signal, and additional means to sense DTMF signals arriving from the calling party. A proper combination of DTMF signals will actuate switching means to enable the (F) to be connected to the telephone line and (A) to be disconnected from the telephone line. In order to actuate (F), a ring generating circuit is initially connected to (F). Thus, the system of Hashimoto may be viewed as a type of private branch exchange (PBX). PBX-type switching systems suffer from the necessity for the calling party to perform additional operations normally unnecessary for operation of the individual units attached to the PBX system. For example, some automatically dialing fax machines without complicated trial and error programming would be unable to properly actuate the fax machine in the disclosed Hashimoto system because they are unable to automatically know when to issue the DTMF control signals necessary to connect the receiving fax machine to the telephone line.
Additional systems considered useful in understanding the background and scope of the present invention are described in the following U.S. patents:
______________________________________ 4,723,268 D. Newell et al 2/02/88 4,660,218 K. Hashimoto 4/21/87 4,623,758 M. Batla et al 11/18/86 4,392,023 M. Sears 7/05/83 4,353,097 T. Takeda et al 10/05/82 4,350,848 M. Kariya et al 9/21/82 4,321,429 T. Takatsuki et al 3/23/82 4,009,342 F. Fahrenschon et al 2/22/77 3,517,137 M. Ribner 6/23/70 3,475,557 C. Morse et al 10/28/69 ______________________________________
None of these references, taken individually or in combination, is considered to exhibit the beneficial features and advantages afforded by the instant invention.
Therefore, an object of this invention is to enable any of a large selection of otherwise incompatible (F), (A), and (T) telephone devices to be connected to a single telephone line in such a manner as to ensure harmonious operation of each of the devices.
Another object of the invention is to enable the composite system to operate such that with respect to a first device, the presence of the additional devices is virtually invisible. In other words, the modes and methods of operating the first device when connected in the composite system will be essentially the same as the modes and methods of operating the same device without the composite system and additional devices.
Another object of the invention is to provide a universal interface capable of connecting a variety of (F), (A), and (T) devices of diverse manufacturers to a single telephone line, without requiring a plurality of interface apparatus designed specifically for an individual model or make of (F), (A), or (T) device.
Another object of the invention is to accomplish the above objects with an inexpensive electronic interface that compares favorably with the long term cost of adding additional telephone lines for each of the normally incompatible devices.
These and further objects and features of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings.